Microscope fine focus control mechanism

ABSTRACT

A monoaxial adjusting system is provided for accomplishing both coarse and fine focusing adjustments between the nosepiece and stage of a microscope. The coarse adjustment is made by rotation of either of two coarse adjusting knobs which in turn directly rotates a coarse adjusting shaft and cam. Suitable linkage is connected to the cam to affect linear movement between the nosepiece and stage. Fine adjustment is made through rotation of either of two fine adjusting knobs which actuate the coarse shaft and cam through a planetary gear reduction system and follower. A further adjusting mechanism is lever operated so that the operator may easily provide fine adjustment while manipulating the North-South stage and East-West slide control knobs. The entire adjusting system is spring and gravity loaded to eliminate backlash.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is cross-referenced to concurrently filed applicationSer. No. 385,424, filed June 7, 1982 entitled "Mechanism forAccomplishing Coarse and Fine Adjustments in a Microscope" for InventorHenry J. Emmel, now patent no. 4,445,758.

BACKGROUND OF THE INVENTION

This invention relates in general to mechanical movements for providingfocusing adjustment to microscopes and, more particularly, to amonoaxial coarse and fine adjusting mechanism which enables the operatorto accomplish coarse and fine focusing when viewing and scanning slides.

DESCRIPTION OF THE PRIOR ART

In the past various methods have been used for providing coarse and fineadjustments in microscopes. Some are accomplished by moving the stagerelative to the nosepiece while others move the nosepiece, relative tothe stage. Examples of microscopes having coarse and fine adjustingmechanisms for providing adjustment to the nosepiece are illustrated anddescribed in U.S. Pat. Nos. 3,135,817 issued June 2, 1964 to N. ARigglesworth et al and 3,260,157 issued July 12, 1966 to O. W. Boughton.An example of a microscope having a stage adjusting mechanism may befound in U.S. Pat. No. 4,083,256 issued Apr. 11, 1976 to M. Shio.

The microscope adjusting mechanism shown by Rigglesworth is a compoundcam and associated linkage wherein the cam would be rotated toaccomplish coarse adjustment of the nosepiece. The cam would then beaxially translated for fine adjustment. The patent to Boughton similarlydiscloses a cam which is rotated for coarse adjustment and axiallytranslated to accomplish fine adjustment.

A further example of another type of microscope focusing mechanism isdisclosed in U.S. Pat. No. 3,768,885 issued Oct. 30, 1973 to O. W.Boughton et al. The coarse-fine focusing mechanism for this microscopediscloses a movable nosepiece which is connected to a linkage that is indirect engagement with a rotatable cam. The cam is rotated by areduction gear system for fine adjustment. Both the cam and gear systemare rotated together in order to accomplish coarse adjustment. Thereduction gear system is comprised of a plurality of gears and pinionsenclosed in a gear box. Costly precision parts are required forpreventing backlash in this adjusting system.

Further examples of various other microscope adjusting systems may befound in U.S. Pat. Nos. 3,683,704, 4,020,705 and 4,173,902.

The systems coarse-fine adjusting described in the patents cited aboveare generally rather complicated and, accordingly, expensive tomanufacture.

SUMMARY OF THE INVENTION

This invention is directed toward a mechanism for providing fine focusadjustments to microscopes Basically, a hub with an eccentric bushing isfitted between the coarse-fine shafts and the support column of themicroscope in such a manner that if the hub and eccentric bushing isrotated, the coarse-fine shaft will be displaced vertically a limitedamount such that fine focusing of the nosepiece can be accomplished. Anactuating lever may be affixed to the hub to enable the microscope userto easily grasp the lever between his fingers while simultaneouslymanipulating the stage (N-S) and slide (E-W) adjust knobs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a microscope having a coarse-fine focuscontrol mechanism;

FIG. 2 is a partial plan view in section taken along line 2--2 of FIG.1;

FIG. 3 is a perspective view of the gear follower and biasing mechanism;and

FIG. 4 is a sectional view taken along line 4--4 of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a microscope 10 comprises a base 12, a supportcolumn 14, and eyepiece 16, a nosepiece 18, a plurality of objectives 20and a stage 22. A coarse-fine adjusting mechanism 24 is supported by thecolumn 14 and may be mechanically coupled to either the nosepiece 18 orthe stage 22 by any appropriate mechanism such that rotation of themechanism 24 provides relative adjustment between the nosepiece 18 andthe stage 22.

FIG. 2 illustrates the relationship between the microscope supportcolumn 14 and the coarse-fine adjusting mechanism 24. The mechanism 24comprises a fine shaft 26 which has a pinion 28 formed at one endthereof. A coarse shaft 30 is coaxially mounted about fine shaft 26 andis provided for imparting gross adjustment to the instrument. A cam 23and appropriate linkage 25 are coupled to the adjusting mechanism 24 sothat rotation of the mechanism and cam provides linear movement to thelinkage which in turn provides relative adjustment between the stage andthe eyepiece.

The fine adjusting shaft 26 has adjusting knobs 32 and 34 fixed atopposite ends in any appropriate manner so that rotation thereof alsocauses the shaft 26 to rotate. Asecond set of knobs 36 and 38 isconnected to coarse adjusting shaft 30. Knob 38 is positively affixedfor direct rotation of the shaft 30, while knob 36 is mounted in amanner to be more fully explained later in this description.

A bearing support collar 40 is fixed within bore 42 of support column14. Collar 40 has a boss 44 with a bore 46 which is sized so that it maybe slipped over shaft 30. Knob 36 has a bore 45 which is sized toreceive boss 44 of bearing collar 40 so that friction surface 47 of knob36 may be placed in close proximity to a corresponding friction surface49 of collar 40. A clutch washer 48 is positioned between the frictionsurfaces 47 and 49. A coil spring 50 is positioned about bearing boss44. One end bears against surface 52 of knob 36 while the other end isheld by a washer/retainer assembly 54 which is secured to boss 44. Thespring 50 thereby exerts pressure between the washer/retainer assembly54 and the knob 36 which frictionally engages the clutch washer 48between the friction surfaces 47 and 49. The knob 36 therefore isfrictionally engaged to the bearing collar 40, which is held firmly inplace in support column 14, and may not rotate unless a rotational forceis applied either directly to it or to the other coarse knob 38. Thecoarse knobs will not rotate when the fine knobs are being rotated.

A gear follower member 58 is securely attached near the end 60 of thecoarse shaft 30 and has a ramped surface 62, as best seen in FIG. 3,which will be more fully explained hereinafter.

A cluster gear and pinion assembly 64 comprises a cluster gear 66, ashaft 68 and a cluster pinion 70. Assembly 64 is positioned so that theshaft 68 is positioned across and bears against the ramped surface 62 offollower member 58 as illustrated in FIGS. 2 and 3. Cluster gear 66engages pinion 28 while cluster pinion 70 engages coarse knob ring gear72 provided on an internal surface of knob 36. In order to hold theshaft 68 against the ramp surface 62, the cluster gear 66 in engagementwith the pinion gear 28 and the cluster pinion against ring gear 72, apair of biasing springs 74 and 76 provided. One of the springs, coilspring 74, extends from a cluster gear shaft extension 78 to retainingpost 80 on gear follower member 58. The other spring, cantilever spring76, is secured to follower member 58 by, for instance, screws 84 so thatit bears against the shaft 68 near the pinion gear 70. In this mannerthe springs exert pressure against the shaft 68 so that the shaftessentially self-centers itself on the ramped surface 62 of gearfollower member 58 and so that pinion gear 70 is properly received by,and preloaded into, ring gear 72. The cluster gear shaft 68 may movesubstantially radially on the ramped surface 62 to find properalignment. Thus, the critical dimensioning necessary in nearly allmicroscopes featuring planetary gear systmems has effectively beeneliminated. Cluster gear 66 is similarly held in position and loadedagainst pinion 28 by spring 74.

A hub 92 is fitted to shaft 30 and is positioned between coarse knob 38and support column 14. As illustrated in FIGS. 2 and 4, hub 92 has abore 94 which is journaled about coarse shaft 30. Further, as explainedmore fully hereinafter, it has a tapered bushing 96 which is eccentricapproximately 0.005" to bore 94 along axis 98 as best seen in FIG. 4. Aslot 100 is formed in the hub 92 concentric to bore 94 and extends overan arc of approximately 40°. A stop member 102 is positioned on thesupport column 14 so that it is received in slot 100. A lever 104 isaffixed to the hub 92 and extends in a direction generally toward thefront of the microscope. Stop member 102 has a spring and washerassembly 106 mounted thereto which presses hub 92 against a frictionwasher 93 which is positioned between the column 14 and hub 92. Thisarrangement acts to resist rotation of the hub 92 when the coarse shaft30 is rotated. However, this clutch effect may be overcome by theoperator merely rotating the lever 104.

As is evident from FIG. 2, the tapered bushing 96 of hub 92 forms one ofthe conical bearings provided to support the coarse shaft 30 withrespect to the support column 14. It is received in an accommodatingconical bore 108 of support column 14. A second conical bearing 110 isfitted to accommodating conical bore 112 of bearing support collar boss44.

An additional conical bearing 114 is fitted to bore 116 to support oneend of fine shaft 26. A thrust washer 117 is fitted to the shaft 26 andholds the bearing 114 in place. The conical bearing 114 eliminatesradial movement between fine shaft pinion 28 and coarse shaft 30. Theopposite end of the fine shaft 26 has no critical rotationalrelationship to any adjustments that may be made and, may therefore,have a much simplier spacer bearing 118 which may be fitted between fineshaft 26 and coarse shaft 30. It has been found that the conicalbearings, as well as the spacer bearing work extremely well if they aremanufactured from a material such as acetal.

In order to provide a system for supporting the coarse-fine shafts thatessentially self adjusts allowing for both loose tolerances and wear,tapered bushing 96 and conical bearings 110 and 114 are split, such asis shown by 120 in FIG. 3. A coil spring 122 is fitted about coarseshaft 30 and exerts pressure between tapered bushing 96 and coarse knob38 which is firmly attached to shaft 30. Another coil spring 124 isfitted about fine shaft 36 and exerts pressure between spacer bearing118 and knob 34. It will be appreciated that these springs exertpressure essentially axially and therefore, spring load the bearingsinto their accommodating bores. The bearings may either expand orcollapse about the shafts until a proper fit between the bearing andshaft is achieved. If either of the shafts vary in diameter, the splitbearings are able to automatically accommodate for variations in shaftdiameter and for radial wear.

In operation a slide 122 is positioned on the stage 22 and one of thecoarse adjusting knobs 36 or 38 is rotated to brong the slide intoapproximate focus. It will be appreciated that in order to rotate eitherof the coarse knobs, the frictional engagement that exists between knob36 and clutch washer 48 must be overcome.

When knob 38 is rotated, it directly rotates the coarse shaft 30. Knob36, however, is not directly mounted to the shaft 30. Instead, itrotates the shaft through the cluster gear and pinion assembly 64 andthe gear follower 58. That is, when the knob 36 is directly rotated bythe operator, it drives the cluster gear and pinion assembly 64, becausethe cluster pinion 70 is in mesh with the knob ring gear 72. The gearfollower 58 is driven by the cluster gear shaft 68 and, consequently,rotates the coarse shaft 30 to which it is directly mounted.

When the coarse adjustment has been accomplished the operator would thenrotate either of the fine adjusting knobs, 32 or 34, which causesrotation of the fine shaft pinion 28. The cluster gear and pinionassembly 64 which is in engagement with the pinion 28 would then alsorotate. However, the frictional engagement between coarse knob 36 andclutch washer 48, explained hereinabove, is sufficient to preventrotation of the coarse knob 36 by pinion gear 70. Thus, gear 70 acts asa planet gear rotating in mesh with ring 72. The gear follower member 58is controlled by the cluster gear shaft 68. Therefore, when the shaft 68rotates with gear 70 it also rotates the gear follower 58. However, theamount of rotation is only proportional. That is, where one revolutionof either of the coarse knobs rotates the coarse shaft one revolution,one revolution of either of the fine knobs only causes the cluster gearand pinion assembly, which drives the gear follower 58, to rotate thecoarse shaft approximately 1/60th of a turn.

This system prevents backlash from occurring in the adjusting systemthrough the use of the cluster gear and pinion assembly, gear followerand spring biasing arrangement. Backlash is also prevented as thelinkage 25 which rests on the cam 23 provides a gravity method ofloading the adjusting system.

In the past when adjusting the (N-S) knob 124 and the (E-W) knob 126 sothat a slide 122 could be scanned, it was necessary to position the handin a very awkward manner so that the desired knob could be rotated witha thumb and forefinger, while simultaneously, and continually, rotatingthe fine focus knob 34 with one of the remaining fingers. To overcomethis difficulty, the hub 92 has been provided with the aforementionedlever 104 which the operator can easily position between the third,fourth or fifth fingers, as best seen in FIG. 1. In this fashion theoperator would still have use of the thumb and forefinger for rotatingknobs 124 and 126 while scanning the slide. The operator may now easilymove the lever 104, either in an upward or downward arc of approximately40°. This lever movement causes the hub 92 to rotate. Because taperedbushing 96 is 0.005" eccentric, as previously described, movement of thelever 104, for instance, through the full 40° causes the shaft 30 tovertically raise or lower (as indicated by "X" and "Y" ) in FIG. 2approximately 0.002". This vertical movement of the shaft 30 translatesinto a vertical adjustment of ±0.001" at the objective as the cam ispositioned approximately midway on the shaft. It should be understoodthat the orientation of the bushing 96 with respect to the column 14 hasbeen selected such that a maximum vertical component is imparted to theshaft 30 when the hub 92 is rotated. This vertical movement, even thoughslight, is more than sufficient to allow for the continual fineadjustment needed to the maintained while scanning slides.

Therefore, in effect, the rotation of the hub 92 by the operator causesthe coarse shaft 30 to pivot about the split conical bearing 110 whichcauses the cam to raise or lower. Obviously, the position of the hub 92has been selected so that when the lever 104 is rotated in an upwardmanner, the cam also moves upward. Similarly, downward rotation of thelever moves the cam downward.

From the foregoing, it will also be appreciated that the eccentricbushing arrangement could be fitted to a microscope which has a singleadjusting shaft. This single shaft would be rotated directly, as in anormal microscope, to provide the coarse adjustment. The eccentricbushing, which would be fitted between the column and shaft, would berotated to provide fine adjustment. There would be no need for theassociated, and sometimes complicated, normal gear reducing systems forproviding fine adjustments. Sufficient movement can be provided by useof the eccentric bushing alone.

The foregoing description is given by way of example only and should notbe considered a limitation. It is contemplated that changes andmodifications may be made in the present invention without departingfrom the spirit or scope thereof.

What is claimed is:
 1. In an optical instrument having a support and anadjusting system supported thereby, said system having at least oneshaft and mechanism cooperatively engaged thereto for providing relativemovement between the instrument's optics and an object being examined, afine focusing control mechanism comprising:a rotatable membereccentrically positioned between said at least one shaft and saidsupport for accomplishing fine focusing whereby rotation of saidrotatable member displaces said at least one shaft with respect to saidsupport a sufficient amount such that said mechanism imparts finefocusing movement.
 2. The optical instrument fine focusing controlmechanism as set forth in claim 1, wherein said rotatable membercomprises an eccentric bushing and includes projection means on saidbushing to enable the operator to readily grasp said projection means torotate said eccentric bushing.
 3. The optical instrument fine focusingcontrol mechanism as set forth in claim 2, wherein said projection meanscomprises an actuating lever.
 4. The optical instrument fine focusingcontrol mechanism as set forth in claim 1, wherein stop means isprovided for cooperative engagement between said support and saidrotatable member whereby said stop means prevents said rotatable memberfrom rotating past a preselected point.
 5. The optical instrument finefocusing control mechanism as set forth in claim 4 wherein said stopmeans comprises a pin projecting from said support column and beingreceived within a slot formed in said rotatable member.
 6. The opticalinstrument fine focusing mechanism as set forth in claim 5, and futherincluding friction means for cooperative engagement between said columnand said rotatable member whereby rotation of said rotatable member isprevented when said at least one shaft is rotated by knobs affixedthereto yet being rotatable when force is applied directly thereto. 7.The optical instrument fine focusing system as set forth in claim 6,wherein said friction means is affixed to said projecting pin.